How far to push on duty cycle
06-29-2015, 08:44 AM
#1
How far to push on duty cycle Cars on pump e85.
Twin 62mm turbos ls 365 19psi.
Base fuel pressure set at 60psi with 1:1 fuel regulator
FIC ls9 112lbr injector at 60psi
Eboost 2 controller set on momentary switch to increase boost levels 8,13,19
Walbro 340 in stock tank with stand alone magnafuel 4703 fuel system boost activated at 2psi. Weth injected at 12.8psi 15gph pre intercooler 7gph post.
Never get to stay wot at 19psi as afr goes from 11.9 @13PSI as third stage comes in afr goes up to 13.0-13.1 duty cycle goes from 83% to 118% with lean afr.
shooting for 8.6s this yr.
Cars been 9.0 @153mph with 1.40 60ft
9.3 @ 158 with 1.77 60ft, both runs at 19psi looking to go up to 26-28psi..
what size injector do I need to go to for my goals.
Thanks in advance
Twin 62mm turbos ls 365 19psi.
Base fuel pressure set at 60psi with 1:1 fuel regulator
FIC ls9 112lbr injector at 60psi
Eboost 2 controller set on momentary switch to increase boost levels 8,13,19
Walbro 340 in stock tank with stand alone magnafuel 4703 fuel system boost activated at 2psi. Weth injected at 12.8psi 15gph pre intercooler 7gph post.
Never get to stay wot at 19psi as afr goes from 11.9 @13PSI as third stage comes in afr goes up to 13.0-13.1 duty cycle goes from 83% to 118% with lean afr.
shooting for 8.6s this yr.
Cars been 9.0 @153mph with 1.40 60ft
9.3 @ 158 with 1.77 60ft, both runs at 19psi looking to go up to 26-28psi..
what size injector do I need to go to for my goals.
Thanks in advance
06-29-2015, 06:12 PM
#2
You got a couple of options here. First off, who tunes your car? I take it you tune it yourself? If so, great!
First thing I would do is have your local e85 tested. I was in an injector situation recently, and it turned out my local e85 was actually e91. So that won't help our IDC problems at all.
Second, you have plenty of pump, so I would feel perfectly safe with cranking up my base pressure 5-10psi. Then, put that in the tune, and see where that puts you at for IDC.
Third, You are spraying meth WITH e85. You have PLENTY of octane and IAT control for your setup, so the third option would be to cut your fuel down. It can be a little bit of a pain, but doesn't take too long. Cut your e85 down to say e50, or e70, fix the tune, and your IDC values are going to be more than fine.
I had to do a combination of all 3 of these to bandaid my setup to work correctly. For what it's worth, my car can run the time in my sig on e50 with only siemens 80# injectors. I have them at 68psi base pressure. No meth. And they were at like 87% IDC if I recall.
First thing I would do is have your local e85 tested. I was in an injector situation recently, and it turned out my local e85 was actually e91. So that won't help our IDC problems at all.
Second, you have plenty of pump, so I would feel perfectly safe with cranking up my base pressure 5-10psi. Then, put that in the tune, and see where that puts you at for IDC.
Third, You are spraying meth WITH e85. You have PLENTY of octane and IAT control for your setup, so the third option would be to cut your fuel down. It can be a little bit of a pain, but doesn't take too long. Cut your e85 down to say e50, or e70, fix the tune, and your IDC values are going to be more than fine.
I had to do a combination of all 3 of these to bandaid my setup to work correctly. For what it's worth, my car can run the time in my sig on e50 with only siemens 80# injectors. I have them at 68psi base pressure. No meth. And they were at like 87% IDC if I recall.
07-01-2015, 07:24 AM
#3
THANKS for reply 93camaro.
Yes I tune my own car. i was afraid of turning up base to far as for the 1;1 regulator.. Im not sure how high they can get with out clipping the injector? (ls9 rebuilt by FIC)
what kinda timing do you run on e50?. as of now on e85 im only at 16deg on the big end for the street and 19deg at the track..
We have a blinder pump here in town e85 e50 e30 e20. My buddy procharged gs corvette runs e50 and loves it.
I have had the AIS meth kit for yrs just sitting around so I threw it on.. Ii know its over kill but i cant hurt..
Yes I tune my own car. i was afraid of turning up base to far as for the 1;1 regulator.. Im not sure how high they can get with out clipping the injector? (ls9 rebuilt by FIC)
what kinda timing do you run on e50?. as of now on e85 im only at 16deg on the big end for the street and 19deg at the track..
We have a blinder pump here in town e85 e50 e30 e20. My buddy procharged gs corvette runs e50 and loves it.
I have had the AIS meth kit for yrs just sitting around so I threw it on.. Ii know its over kill but i cant hurt..
07-01-2015, 01:10 PM
#4
THANKS for reply 93camaro.
Yes I tune my own car. i was afraid of turning up base to far as for the 1;1 regulator.. Im not sure how high they can get with out clipping the injector? (ls9 rebuilt by FIC)
what kinda timing do you run on e50?. as of now on e85 im only at 16deg on the big end for the street and 19deg at the track..
We have a blinder pump here in town e85 e50 e30 e20. My buddy procharged gs corvette runs e50 and loves it.
I have had the AIS meth kit for yrs just sitting around so I threw it on.. Ii know its over kill but i cant hurt..
Yes I tune my own car. i was afraid of turning up base to far as for the 1;1 regulator.. Im not sure how high they can get with out clipping the injector? (ls9 rebuilt by FIC)
what kinda timing do you run on e50?. as of now on e85 im only at 16deg on the big end for the street and 19deg at the track..
We have a blinder pump here in town e85 e50 e30 e20. My buddy procharged gs corvette runs e50 and loves it.
I have had the AIS meth kit for yrs just sitting around so I threw it on.. Ii know its over kill but i cant hurt..
Keep total pressure under 100psi and you'll be fine. IMO you don't have enough pump or injector for what your attempting on E85. Drop down to e50 or add pump or get a voltage booster for the pump(s).
Anytime the DC is over 100% the injector is wide open and no longer pulsing. If you're hitting 100% DC pushing past this point (110...150% DC) does nothing.
07-01-2015, 07:19 PM
#5
This is not accurate. 100% duty cycle in GM's fuel strategy is roughly the amount of time that the intake valve is open. So this varies at different rpms. At 6000 rpm, it still takes the motor 100ms to go through 4 cycles. At 6000rpm, 100% IDC equates to 20ms injector timing. Obviously GM's idea is to only have the fuel injector spraying when the intake valve is open, but even if the injector sprays a little before or a little after the intake valve event, it's not the end of the world. That's how multi-port fuel inejction worked back in the day. You can even adjust in HpTuners to command the injector event earlier in the 4 stroke cycle under "Injector Timing Boundary." But at 100%, the fuel injector is definitely not static open.
07-01-2015, 07:30 PM
#6
This is not accurate. 100% duty cycle in GM's fuel strategy is roughly the amount of time that the intake valve is open. So this varies at different rpms. At 6000 rpm, it still takes the motor 100ms to go through 4 cycles. At 6000rpm, 100% IDC equates to 20ms injector timing. Obviously GM's idea is to only have the fuel injector spraying when the intake valve is open, but even if the injector sprays a little before or a little after the intake valve event, it's not the end of the world. That's how multi-port fuel inejction worked back in the day. You can even adjust in HpTuners to command the injector event earlier in the 4 stroke cycle under "Injector Timing Boundary." But at 100%, the fuel injector is definitely not static open.
Duty cycle is calculated as PW*RPM/1200 = Duty Cycle (%). No where in there is intake valve open time. It has to do with the calculated pulsewidth time vs the available time in the combustion cycle.
The changing of the eoit is so you can more accurately fire the injector at low pulsewidth/duty cycle.
100% duty cycle is 100% of the time it takes for the engine to complete 2 revs (1 combustion cycle).
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07-02-2015, 07:51 AM
#9
What is "clipping the injector" ?
Keep total pressure under 100psi and you'll be fine. IMO you don't have enough pump or injector for what your attempting on E85. Drop down to e50 or add pump or get a voltage booster for the pump(s).
Anytime the DC is over 100% the injector is wide open and no longer pulsing. If you're hitting 100% DC pushing past this point (110...150% DC) does nothing.
Keep total pressure under 100psi and you'll be fine. IMO you don't have enough pump or injector for what your attempting on E85. Drop down to e50 or add pump or get a voltage booster for the pump(s).
Anytime the DC is over 100% the injector is wide open and no longer pulsing. If you're hitting 100% DC pushing past this point (110...150% DC) does nothing.
my pump i way more then enough.. capable of 2500HP
07-02-2015, 12:42 PM
#10
2. The differential pressure is what's important. 60psi fuel pressure, 19psi boost pressure results in an effective fuel pressure of 40psi. The resultant 40psi is what will "clip" your injector if it goes too high.
07-10-2015, 06:10 PM
#12
9 Second Club
You need more injector, plain and simple.
Chances are that 2500hp pump....at efi pressures will probably barely be a 1500hp, if you're lucky...on pump fuel.
And I'd imagine if you tried to run either pump at 100psi total, they'd both have a fit and flow **** all.
As for ecu's reporting 118% IDC, of course it is nonsense but it is a calculated value so correct for what it is telling you mathematically. Either way, it's telling you loud and clear you need more fuel flow.
And most decent modern injectors will be quite happy at higher pressures, more so than your pumps will be IMO.
Chances are that 2500hp pump....at efi pressures will probably barely be a 1500hp, if you're lucky...on pump fuel.
And I'd imagine if you tried to run either pump at 100psi total, they'd both have a fit and flow **** all.
As for ecu's reporting 118% IDC, of course it is nonsense but it is a calculated value so correct for what it is telling you mathematically. Either way, it's telling you loud and clear you need more fuel flow.
And most decent modern injectors will be quite happy at higher pressures, more so than your pumps will be IMO.
07-19-2015, 12:28 AM
#13
sorry for such a long time for reply.
340 intake pump runs factory line to where the stock filter is located then ties into 10an feed line that is supplied by big pump.
intake pumps runs 100% time as the big pump is boost referenced, Big pump is good to 120psi as i never plan on getting any where near that. as for the intake pump im afraid that the big pump will start to back feed through the lil pump as pressure gets to high.
Looking for 160-220 injectors now
340 intake pump runs factory line to where the stock filter is located then ties into 10an feed line that is supplied by big pump.
intake pumps runs 100% time as the big pump is boost referenced, Big pump is good to 120psi as i never plan on getting any where near that. as for the intake pump im afraid that the big pump will start to back feed through the lil pump as pressure gets to high.
Looking for 160-220 injectors now